VSKYLABS 902X-NTR - This Document is a Work-in-Progress
FOR INFORMATION ONLY - FLIGHT SIMULATION USE ONLY DO NOT USE FOR REAL FLIGHT
VSKYLABS ‘Test-Pilot’: 902X-NTR
MANUAL / POH
Rev 0.03 (November 2025)
Special Development Notice:
The VSKYLABS 902X-NTR simulation add-on for X-Plane flight simulator is an independent VSKYLABS development effort which is not related nor affiliated with 'MD Helicopters' or any other company or entity.
Although the VSKYLABS 902X-NTR simulation is derived from, and highly inspired by the real-world MD-902 reference alongside its technical/theoretical design specs, it is not intended, by concept, to be an exact replica nor an official simulation of the MD-902.
VSKYLABS Aerospace Simulations / Copyright Ⓒ2025 JetManHuss - VSKYLABS. All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law. For permission requests, write to the publisher, addressed “Attention: Permissions Coordinator,” at the following address: contact@vskylabs.com
REFERENCE MATERIALS
MD-902 ROTORCRAFT FLIGHT MANUAL (RFM)
For those seeking additional insights into the technical aspects and operational characteristics of a real-world No Tail Rotor (NTR) helicopter, the MD-902 Rotorcraft Flight Manual (RFM) is available online as a reference.
This manual provides information on the MD-902’s systems, flight performance, and operational procedures, serving as a useful educational resource for understanding the design principles of a twin-turbine NTR helicopter.
While the VSKYLABS 902X-NTR is not an exact replica of the MD-902, users may find the performance data, fuel consumption figures, and aerodynamic principles outlined in the MD-902 manual to be a valuable general reference when evaluating aspects of the 902X-NTR’s performance envelope.
This manual provides information on the MD-902’s systems, flight performance, and operational procedures, serving as a useful educational resource for understanding the design principles of a twin-turbine NTR helicopter.
While the VSKYLABS 902X-NTR is not an exact replica of the MD-902, users may find the performance data, fuel consumption figures, and aerodynamic principles outlined in the MD-902 manual to be a valuable general reference when evaluating aspects of the 902X-NTR’s performance envelope.
Important Disclaimer:
- The MD-902 RFM is an external document, unrelated to VSKYLABS.
- The provided link is for educational and informational purposes only.
- VSKYLABS is not responsible for the content, accuracy, or availability of this manual.
- The VSKYLABS 902X-NTR is not an official or exact simulation of the MD-902.
INTRODUCTION
WHAT EXACTLY IS THE VSKYLABS 902X-NTR?
The VSKYLABS 902X-NTR was developed as part of VSKYLABS' educational, experimental, and engineering initiatives. This project aims to deliver a highly engineered, physics-based simulation of a twin-turbine No Tail Rotor helicopter test-bed.
To create a plausible NTR helicopter simulation, VSKYLABS focused on the MD-902 as a general reference, leveraging its technical aspects and system architecture as a baseline for a typical twin-turbine No-Tail-Rotor helicopter design.
While the VSKYLABS 902X-NTR is inspired by and derived from the MD-902's real-world specifications, it is not an exact replica nor an official simulation of the MD-902.
In line with the project’s goals and inherent development constraints, the VSKYLABS 902X-NTR features several differences from the MD-902. These may include variations in performance, subsystems, and other design elements.
To create a plausible NTR helicopter simulation, VSKYLABS focused on the MD-902 as a general reference, leveraging its technical aspects and system architecture as a baseline for a typical twin-turbine No-Tail-Rotor helicopter design.
While the VSKYLABS 902X-NTR is inspired by and derived from the MD-902's real-world specifications, it is not an exact replica nor an official simulation of the MD-902.
In line with the project’s goals and inherent development constraints, the VSKYLABS 902X-NTR features several differences from the MD-902. These may include variations in performance, subsystems, and other design elements.
TWO VARIANTS ARE INCLUDED: VSL 902X-NTR / VSL 902eX-NTR:
The project includes two different variants:
- 902X-NTR- The main NTR test-bed prototype.
- 902eX-NTR - The Extended-Range/Heavy NTR prototype.
VSL 902X-NTR
VSL 902eX-NTR - Extended Range Variant (above)
VSKYLABS 902eX-NTR Variant:
The VSL 902eX-NTR variant is an ‘Extended-Range’, heavy test-bed prototype. It features two external (fixed) fuel tanks, each is capable of carrying 865 lbs of Jet-A fuel (~130 US Gallons, ~488 Liters, ~392 Kgs). The additional fuel tanks increase the on-board fuel capacity from 1,025 lbs (basic internal fuel-tank) to 2,755 lbs. That is, from ~580 liters to ~1,556 liters).
MTOW of the VSL 902eX-NTR is 6,770 lbs, similar to the published MTOW of the MD-969 - a proposed attack helicopter which is based on the MD-902 Explorer.
The external fuel tanks are pressurized, feeding the internal fuel-tank. Feeding can be enabled in separate or in parallel. The external fuel tanks system includes an equalization valve which keeps symmetrical load during parallel transfer.
Depending on flight profile - Test flights demonstrated range capability of nearly 800 NM (no wind, ISA, 8,000 feet Long-Range-Cruise).
MTOW of the VSL 902eX-NTR is 6,770 lbs, similar to the published MTOW of the MD-969 - a proposed attack helicopter which is based on the MD-902 Explorer.
The external fuel tanks are pressurized, feeding the internal fuel-tank. Feeding can be enabled in separate or in parallel. The external fuel tanks system includes an equalization valve which keeps symmetrical load during parallel transfer.
Depending on flight profile - Test flights demonstrated range capability of nearly 800 NM (no wind, ISA, 8,000 feet Long-Range-Cruise).
NOTAR ® anti-torque system (MD-902 reference vs VSKYLABS 902X-NTR):
The NOTAR® anti-torque system utilizes helicopter aerodynamics to deliver safe, quiet, and FOD-resistant directional control. This is achieved by using a variable-pitch composite fan to pressurize the tailboom with ambient air, which is then expelled through slots on the right side, producing the “Coanda Effect.” This effect transforms the tailboom into a lift-generating surface, providing up to 70% of the required anti-torque during a hover. A rotating thruster manages the remaining anti-torque requirements. During forward flight, vertical stabilizers provide the majority of the anti-torque, while the thruster maintains directional control. By eliminating the need for drive shafts, bearings, and gearboxes, the NOTAR system overcomes the mechanical drawbacks associated with a traditional tail rotor.
VSKYLABS 902X-NTR physics-based anti-torque simulation:
The VSKYLABS 902X-NTR anti-torque simulation includes a dedicated NTR jet-fan, which is being simulated as an integrated, interactive two-spool jet engine in X-Plane 12. While the MD-902 NOTAR fan controls boom air-pressure with the use of variable-pitch blades, which are interconnected to the pedal and the collective system, the VSKYLABS 902X-NTR jet-fan manages its RPM, following torque sensors and pedal ‘request’.
The VSKYLABS 902X-NTR jet-fan is coupled with the main transmission, being fully automated during start-up, flight and shut-down.
The VSKYLABS 902X-NTR Direct-Jet-Thruster is a physics-based thrust vectoring nozzle which directs the NTR jet-fan following pedal input.
Both the MD-902 NOTAR fan and the VSKYLABS 902X-NTR jet-fan manage airflow and pressure, thus VSKYLABS 902X-NTR jet-fan responsiveness replicates the delays and response of the MD-902 NOTAR fan operation, resulted with a plausible ‘feel’, compared to a conventional tail-rotor responsiveness and control characteristics.
The VSKYLABS 902X-NTR jet-fan is coupled with the main transmission, being fully automated during start-up, flight and shut-down.
The VSKYLABS 902X-NTR Direct-Jet-Thruster is a physics-based thrust vectoring nozzle which directs the NTR jet-fan following pedal input.
Both the MD-902 NOTAR fan and the VSKYLABS 902X-NTR jet-fan manage airflow and pressure, thus VSKYLABS 902X-NTR jet-fan responsiveness replicates the delays and response of the MD-902 NOTAR fan operation, resulted with a plausible ‘feel’, compared to a conventional tail-rotor responsiveness and control characteristics.
VSKYLABS 902X-NTR - Simulating Coanda effect:
X-Plane would not simulate the actual Coanda effect (in general, and due rotor downwash). In the MD-902 NOTAR, most of the air-flow comes from within the tail-boom, out of the side slots. This cannot be simulated in X-Plane.
To achieve a plausible Coanda effect simulation, based on various factors that are part of the VSKYLABS 902X-NTR simulation, the 'Coanda effect' is being added as a measured and regulated force, simulated and managed to work together with all other components. It interacts with the VSKYLABS 902X-NTR jet-fan which produces the base simulated 'pressure' and thrust.
The simulated VSKYLABS 902X-NTR Coanda effect produces the single-side 'pull' due to all factors.
To achieve a plausible Coanda effect simulation, based on various factors that are part of the VSKYLABS 902X-NTR simulation, the 'Coanda effect' is being added as a measured and regulated force, simulated and managed to work together with all other components. It interacts with the VSKYLABS 902X-NTR jet-fan which produces the base simulated 'pressure' and thrust.
The simulated VSKYLABS 902X-NTR Coanda effect produces the single-side 'pull' due to all factors.
VSKYLABS 902X-NTR FAST GUIDE
INTERACTION AND VR:
The VSKYLABS 902X-NTR is fully interactive and supports full VR experience and operations. All systems, cockpit switches, flight controls and interactive features are accessible via touch controllers operations.
JOYSTICK AND HARDWARE ASSIGNMENT:
The VSKYLABS 902X-NTR includes the VSKYLABS ‘Cockpit-Builders Heaven’ layer, which allows assigning all aircraft switches, knobs, levers, and interactions in a designated, uncluttered section in the X-Plane 12 assignment screen.
To use it for key/button assignments, simply type ‘902’ or a combination, for example: ‘902 main power’ in the search bar and select your assignment. Here is a sample screenshot:
To use it for key/button assignments, simply type ‘902’ or a combination, for example: ‘902 main power’ in the search bar and select your assignment. Here is a sample screenshot:
BEFORE WE START - ENGINE/THROTTLE CONTROLS
MD-902 Automatic vs. Manual Throttle Modes:
The MD-902 is equipped with Pratt & Whitney 207E engines, controlled by a Full Authority Digital Engine Control (FADEC) system. The throttle system operates in two primary modes:
- Automatic Throttle Mode - SIMULATED MODE.
- In normal operations, the throttle is set to FLY, allowing FADEC to automatically manage engine power.
- FADEC adjusts fuel flow, power output, and engine response to maintain optimal rotor speed and engine performance.
- Automatic protections are in place to prevent over-speed, over-temperature, or over-torque conditions.
- Manual Throttle Mode - NOT SIMULATED IN CURRENT VERSION.
- If FADEC fails or is turned off, the pilot must manually control the throttle to maintain engine power.
- Manual throttle operation is activated via the Throttle Twist Grip on the collective control.
- In this mode, engine parameters must be carefully monitored, as there are no automatic protections for over-speed, over-temp, or over-torque.
How does this come in practice?
The MD-902 is designed for effortless engine management, thanks to its FADEC system. Engine operation is as simple as:
The MD-902 is designed for effortless engine management, thanks to its FADEC system. Engine operation is as simple as:
1️⃣ OFF → IDLE (for engine start)
2️⃣ IDLE → FLY (FADEC takes over)
3️⃣ That’s it! - No manual throttle adjustments needed in normal operations.
2️⃣ IDLE → FLY (FADEC takes over)
3️⃣ That’s it! - No manual throttle adjustments needed in normal operations.
The FADEC system handles everything, ensuring smooth power transitions and reducing pilot workload to near push-button simplicity.
VSKYLABS 902X-NTR COCKPIT AND SYSTEMS
The decision to use a glass cockpit display followed the current trend in real-world MD902s. However, it became clear that something was lacking. The all-glass cockpit did provide complete flight data, but it lacked the easy-to-read characteristics of analog instruments in dynamic situations.
The reduced ‘easy-to-read capability’ of flight data especially during maneuvers was pronounced in the VR environment, where the glass display became a limitation because it was difficult to track various ‘handy’ flight data in peripheral vision, such as reading VSI during VFR and low-altitude dynamic flight.
As a result, it was determined that crucial analog gauges, including the radar-alt gauge with its aural and warning light features, should be placed as high as possible on the front panel.
The result provided a good balance between functionality, display options and readability of vital flight data information during flight.
The reduced ‘easy-to-read capability’ of flight data especially during maneuvers was pronounced in the VR environment, where the glass display became a limitation because it was difficult to track various ‘handy’ flight data in peripheral vision, such as reading VSI during VFR and low-altitude dynamic flight.
As a result, it was determined that crucial analog gauges, including the radar-alt gauge with its aural and warning light features, should be placed as high as possible on the front panel.
The result provided a good balance between functionality, display options and readability of vital flight data information during flight.
FRONT PANEL - (Both 902X/902eX-NTR VARIANTS):
IIDS:
The Integrated Instrument Display System (IIDS) provides aircraft system performance data and caution/warning messages via a color LCD. It displays normal conditions in green, cautions in yellow, and warnings in red, with backlighting for visibility in all lighting conditions.
Primary Display: Shows vertical bar and digital readouts for key engine parameters (Np, Nr, torque, and EGT) and includes a two-line alphanumeric display for warnings, cautions, and advisories.
Secondary Display: Includes caution/warning indicators, engine health monitoring, and parameter clusters for transmission and fuel systems.
Computer Functions: Performs automatic engine trend analysis, records exceedances, and provides in-flight rotor and NOTAR® fan balance solutions.
The VSKYLABS 902X-NTR IIDS is a simplified display system which was designed to provide a similar flying experience and engine-data representation.
Primary Display: Shows vertical bar and digital readouts for key engine parameters (Np, Nr, torque, and EGT) and includes a two-line alphanumeric display for warnings, cautions, and advisories.
Secondary Display: Includes caution/warning indicators, engine health monitoring, and parameter clusters for transmission and fuel systems.
Computer Functions: Performs automatic engine trend analysis, records exceedances, and provides in-flight rotor and NOTAR® fan balance solutions.
The VSKYLABS 902X-NTR IIDS is a simplified display system which was designed to provide a similar flying experience and engine-data representation.
IIDS - 902eX-NTR Variant:
The on-board IIDS/Secondary display screen includes additional indications when flying the VSL 902eX-NTR variant.
Fuel quantity indications in LBs include all fuel on-board. When the external fuel tanks are fully consumed, on-board fuel quantity remains 1
Fuel quantity indications in LBs include all fuel on-board. When the external fuel tanks are fully consumed, on-board fuel quantity remains 1
The VSL 902eX-NTR is equipped with a dedicated switches-panel for the external fuel-system. Fuel quantity (left, right, internal) and tank pressurization status are integrated into the IIDS Primary display (only in the eX variant).
PEDESTAL PANEL:
Extended Range Tanks panel:
- Each switch controls the pressurization valve of each tank.
- Pressurization in a given tank is essential for fuel transfer.
- External tanks can only feed the internal tank and do not provide direct fuel to the engines.
- Pressurization modes - single tank pressurization:
- When a single tank is set to ON, fuel will be transferred from the given tank to the internal tank. When the internal tank.
- The unpressurized tank is isolated from the system.
- Pressurization modes - dual tank pressurization:
- This is the normal operation mode of the system.
- When both tanks are pressurized, fuel will be transferred from both tanks to the internal tank.
- A dedicated pressure-valve will manage fuel-level equalization in both external tanks, to avoid asymmetrical consumption.
Engine control switches panel:
- OVSP -This switch/system is part of post-maintenance run-up/trouble-shooting specific systems, not being part of the normal operations checklist. The switch is there however the OVSP test system does not take part in flying the aircraft.
- LH/RH Engine Knobs - Fully functional.
As in the real MD902, the engines operation in ‘auto’ mode is straightforward and simple: - OFF - Shutting off the engine.
- IDLE - Starting up the engine, and for setting it to ‘Idle’ state and RPM.
- FLY - Initiates FADEC control over the engine to maintain 100% Rotor RPM.
- TRAIN - Simulating OEI (One Engine Inoperative). When setting an engine to TRAIN mode, it will be set to ~92% by the FADEC, and will get to ‘standby’ mode. When setting the other engine in TRAIN mode (both engines in TRAIN mode), the system will override the TRAIN mode and both engines will transit to FLY mode, to prevent a situation where both engines are set to ‘Standby’, inflight.
Fuel Systems switches Panel:
- LH/RH Boost pumps - Operates the boost pump for the given engine.
- Fuel Shutoff Valves - Operates the fuel shutoff valves. When set to OFF, each valve arms the extinguisher for the given engine.
- Bottle Discharge - When applied - the fire-extinguishing bottle in the given engine will be initiated, with the condition of the shutoff valve being set to the OFF position. In the VSKYLABS 902X-NTR, only a Primary bottle is available for each engine.
Electrical Systems switches Panel:
- Main power key switch - Located RH side to the pedestal, in front. Main power switch.
- Power BAT/EXT - Battery power switch.
- L/R GEN switches - Engages/disengages the generators for each engine.
- Avionics switch - Switches the Avionics bus, including the G1000 MFD.
Lighting Control switches Panel:
- HUD - Switches the 3-d HUD ON/OFF.
- Strobe, Position - Sets external nav and position lights.
- AREA knob - Off, CAB (cabin lights), CKP (cockpit lights), Both (cabin and cockpit lights).
- Rheostats - Console, Flood, HUD, Instruments.
Utility switches Panels:
- HYD Test sys1/sys2 - Hydraulic systems testing - INOP.
- CAB Heat OVRD - INPO (WIP) - The heating and air conditioning systems are still under development. In the MD902, the AC systems draw power from the engines. If an engine fails, the cabin heating and AC will automatically shut off to give the remaining engine maximum power. Once the pilot has recovered to a safe single-engine flight condition, he can restore cabin heat with the CAB HEAT OVRD position. This is also important for single-engine landings, where CAB HEAT must be OFF to ensure maximum power from the remaining engine.
- Pitot heat - Pitot heat on/off.
- IPS - Inlet Particle Separator - The inlet particle separator is an inertial type particle separator that removes debris from the ambient air before it enters the engine. In the VSL 902X-NTR it works mainly as an inlet anti-icing device, affecting engine power (similar to the inlet anti-ice flap commonly used as Inertial Separator in turbine engines).
- AC/VENT knob - (INOP - it won’t affect your room temperature) The cabin's air conditioning system provides conditioned air and humidity control. Temperature is controlled via a five-position rotary switch (AC/VENT) which includes a high and low setting selected from the center console utility panel assembly.
- VSCS (Vertical Stabilizers Control System) - The system controls the vertical stabilizers using two electro-mechanical actuators, one for each stabilizer. It functions to anticipate power changes, prevent rotor droop, and maximize anti-torque at high speeds. Additionally, it provides yaw damping using yaw gyro/lateral accelerometer signals. A dual indicator on the instrument panel displays the incidence angle of both stabilizers.
Note: In the MD902, the vertical stabilizers are not controlled by the pedals. The pedals are connected to the directional-jet-thruster and the NOTAR FAN blade pitch angle, which control anti-torque, while the vertical stabilizers are being managed by a fly-by-wire stability augmentation system, to provide aerodynamic anti-torque forces and yaw-damping.
The VSKYLABS 902X-NTR VSCS system works the same with one main difference; below ~80 knots, the VSCS system will feed-in pedal inputs on top of the basic VSCS system. These characteristics may be changed in future updates.
- NACA Inlet - Provides ram air to maximize engine performance. In the VSL 902X-NTR, as in real-world MD-902, when there's IPS installed (IPS is optional equipment), then the NACA inlet door opens/closes automatically when exceeding 47 knots. The switch in the cockpit overrides the automatic behavior of the door, setting it in the CLOSED position. However - when a standard inlet screen is installed on the inlet, the NACA inlet door is not even included (it is always open). This is the case in the VSL 902X-NTR.
- Windshield wipers - Two speed wipers actuated by the rotateable knob. The washer switch...VSKYLABS does not provide the windows-cleaning liquid :)
Other - Heat and Defog Systems:
- Foot heater control - (pull-push knob under the front panel, pilot side).
- Cockpit heat control - (pull-push knob pilot side, LH to the collective) - Warm air is ducted forward to two aft−facing nozzles above and forward of the pilots’ feet, and to a pair of nozzles along the bottom of the upper windshield panels to defog them. (operational in the VSKYLABS 902X-NTR).
Other - Rotor Brake:
- Rotor brake lever: The rotor brake lever must be in the stowed (up) position prior to engine starting. The rotor brake may be applied after both engines are shut down with NR at or below 70 percent (The VSKYLABS 902X-NTR does not simulate damage due to rotor-brake abuse. It may be implemented in future updates).
- Indications: Yellow ROTOR BRAKE annunciator ON.
SYSTEMS DESCRIPTION
The VSKYLABS 902X-NTR technical specs are derived from the MD-902, however it was not designed nor intended as a direct replica or an official simulation of the MD-902.
For general reference, here is a short description of the MD-902:
The MD-902 is a twin-engine, multi-purpose helicopter that can accommodate eight passengers. It features a patented NOTAR® anti-torque system and a bearingless, composite, fully-articulated rotor system.
The helicopter's engines are shafted directly to the transmission without a combining gearbox. A single short shaft from the transmission drives the NOTAR® fan, while two quills drive the engine and transmission oil cooling system.
An Integrated Instrumentation Display System (IIDS) monitors and displays powerplants, fuel, hydraulic, and electrical systems to the crew.
The MD-902 is equipped with a non-retractable skid landing gear and energy-attenuating crew and passenger seats. The spacious cabin features large, 52-inch sliding doors on each side, hinged crew doors, and an aft cabin hinged door for baggage or alternate loading.
The VSKYLABS 902X-NTR specifications are derived from the MD-902 design, to allow a solid baseline for a twin-engine no-tail-rotor helicopter design. However, there are various differences in systems and anti-torque layout due various limitations in the simulated environment.
The helicopter's engines are shafted directly to the transmission without a combining gearbox. A single short shaft from the transmission drives the NOTAR® fan, while two quills drive the engine and transmission oil cooling system.
An Integrated Instrumentation Display System (IIDS) monitors and displays powerplants, fuel, hydraulic, and electrical systems to the crew.
The MD-902 is equipped with a non-retractable skid landing gear and energy-attenuating crew and passenger seats. The spacious cabin features large, 52-inch sliding doors on each side, hinged crew doors, and an aft cabin hinged door for baggage or alternate loading.
The VSKYLABS 902X-NTR specifications are derived from the MD-902 design, to allow a solid baseline for a twin-engine no-tail-rotor helicopter design. However, there are various differences in systems and anti-torque layout due various limitations in the simulated environment.
Horizontal and vertical stabilizers:
The fixed composite horizontal stabilizer is designed to minimize airframe vibration caused by wake turbulence. Two composite vertical fins are mounted on the horizontal stabilizer. The vertical fins are aerodynamically trimmed for stable cruise flight, and are controlled by the VSCS (Vertical Stabilizer Control System).
Vertical stabilizer control system (VSCS):
The VSCS is a fly-by-wire control system which controls the vertical stabilizers. Each stabilizer is controlled separately. The VSCS manages the fin incidence with collective pitch to minimize anti-torque power and for optimum fin angle during autorotation. In forward flight it provides yaw-damping and stability augmentation and increasing directional stability during descent.
Tailboom:
The tailboom is a composite tube which incorporates the NOTAR® slots along the right
(starboard) side. It supports the horizontal stabilizer, the two articulated vertical fins, and
the thruster. A tail skid is attached to protect the rotating cone.
(starboard) side. It supports the horizontal stabilizer, the two articulated vertical fins, and
the thruster. A tail skid is attached to protect the rotating cone.
Flight control system:
Flight control is managed by aerodynamically tilting the rotor's tip path plane through cyclic pitch adjustments on the rotor blades, while directional stability is maintained using the NOTAR® anti-torque system in conjunction with variable-pitch vertical stabilizers.
Mechanical NOTAR® controls:
Pilot pedal inputs are transmitted through levers and bellcranks to a single hydraulic boost system, which adjusts the variable-pitch NOTAR® fan blades and positions the direct jet thruster to the desired direction.
Trim system:
The trim system allows the pilot to eliminate longitudinal and lateral stick forces at any position using a multi-position switch on the cyclic grip which activates electromechanical actuators.
Propulsion system:
Two Pratt & Whitney Canada PW207E turboshaft engines, rated at 477 kw (640 shp) each, derated for reliability and safety to: Take-off 410 kw (550 shp) Max Continuous Power 373 kw (500 shp). The engines are situated above the baggage compartment and angled inward to connect with the main transmission gearbox. Each engine is linked to the transmission by a short shaft. The NOTAR fan is driven by a longer shaft fitted with similar couplings.
Engine air intake and Inlet Particle Separator (IPS):
Ambient air enters each engine compressor case inlet through the air intake system. This system includes an inlet screen or an optional inlet particle separator for each engine, which prevents debris from entering the engine ducts.
IPS (simulated in the VSKYLABS 902X-NTR):
The engine's inlet particle separator uses inertia and a vortex to remove debris from the air. If the separator becomes clogged, bypass doors automatically open. In the VSL 902X-NTR it works mainly as an inlet anti-icing device, affecting engine power (similar to the inlet anti-ice flap commonly used as Inertial Separator in turbine engines).
NACA inlet:
Provides ram air to maximize engine performance. In the VSL 902X-NTR, as in real-world MD-902, when there's IPS installed (IPS is optional equipment), then the NACA inlet door opens/closes automatically when exceeding 47 knots. The switch in the cockpit overrides the automatic behavior of the door, setting it in the CLOSED position. However - when a standard inlet screen is installed on the inlet, the NACA inlet door is not even included (it is always open). This is the case in the VSL 902X-NTR.
Main rotor system:
The main rotor is a five bladed, fully articulated hingeless flexbeam system. The rotor diameter is 33.83 feet with a blade chord of 10 inches. At its nominal 100 percent rotational speed (NR), the rotor runs at 392 rpm (695 feet/second tip speed).
Main rotor data:
Number of blades ......................................5
Direction of rotation .................................Counter-clockwise, seen from above
Diameter ...................................................33.8 ft. (10.3 m)
Blade chord................................................0.83 ft (0.25 m)
Disk area ...................................................900 ft2 (83.6 m2)
Disk loading...............................................6.94 lb/ft 2 at maximum weight
Blade tip speed, 100% NR ........................695 FPS
Rotor speed, 100% NR..............................392 RPM
Direction of rotation .................................Counter-clockwise, seen from above
Diameter ...................................................33.8 ft. (10.3 m)
Blade chord................................................0.83 ft (0.25 m)
Disk area ...................................................900 ft2 (83.6 m2)
Disk loading...............................................6.94 lb/ft 2 at maximum weight
Blade tip speed, 100% NR ........................695 FPS
Rotor speed, 100% NR..............................392 RPM
Transmission rating (MD-902 reference):
Take-off ...................................................550 shp (per engine)
Maximum continuous..............................500 shp (per engine)
OEI, continuous.......................................620 shp
OEI, 2.5 minute limit...............................680 shp
Maximum continuous..............................500 shp (per engine)
OEI, continuous.......................................620 shp
OEI, 2.5 minute limit...............................680 shp
Rotor brake:
The rotor brake system is separate and self-contained. It utilizes a master cylinder, controlled by the cockpit brake handle, to engage an actuator. This actuator operates a disc brake located on the transmission. A yellow BRAKE caution annunciator, found on the IIDS secondary display screen, alerts the pilot if the brake is not fully disengaged.
Fuel system:
A single crash−resistant fuel cell is capable of holding 149 U.S. gallons (~452 Kg) of jet fuel and is located in the lower fuselage under the main cabin floor.
As optional equipment, there is an additional auxiliary fuel tank, holding approximately 29.4 US gallons (200 LB, Jet−A, 72 Kg) underneath the baggage compartment floor.
The auxiliary fuel tank is not 'installed' in the VSKYLABS 902X-NTR.
The fuel system panel mounted switches are used by the pilot to control the fuel system. The IIDS displays the fuel level, which is sensed by a forward and an aft probe. When the pressure falls below the acceptable limit, two fuel pressure switches activate caution lights in the IIDS.
As optional equipment, there is an additional auxiliary fuel tank, holding approximately 29.4 US gallons (200 LB, Jet−A, 72 Kg) underneath the baggage compartment floor.
The auxiliary fuel tank is not 'installed' in the VSKYLABS 902X-NTR.
The fuel system panel mounted switches are used by the pilot to control the fuel system. The IIDS displays the fuel level, which is sensed by a forward and an aft probe. When the pressure falls below the acceptable limit, two fuel pressure switches activate caution lights in the IIDS.
Fire extinguishing system:
The pilot can discharge a fire extinguishing agent into the designated engine using the fire extinguishing system. The transmission area does not have a fire extinguishing system.
The fire extinguishing system is armed when the Fuel Shutoff valves are closed. The fire extinguisher bottles are discharged by momentarily switching the BOTTLE DISCHARGE switch to either the primary (PRI) or alternate (ALT) position.
Located on the cockpit FUEL SYSTEM panel between the left and right fuel shutoff valves, the BOTTLE DISCHARGE switch has three momentary positions. The fire extinguishing system for an engine is armed by setting its corresponding fuel shutoff valve to the OFF position. The primary bottle is discharged by selecting PRI, and the secondary bottle is discharged by selecting ALT.
The fire extinguishing system is armed when the Fuel Shutoff valves are closed. The fire extinguisher bottles are discharged by momentarily switching the BOTTLE DISCHARGE switch to either the primary (PRI) or alternate (ALT) position.
Located on the cockpit FUEL SYSTEM panel between the left and right fuel shutoff valves, the BOTTLE DISCHARGE switch has three momentary positions. The fire extinguishing system for an engine is armed by setting its corresponding fuel shutoff valve to the OFF position. The primary bottle is discharged by selecting PRI, and the secondary bottle is discharged by selecting ALT.
Electrical system:
The MD-902 electrical system operates on 28 Vdc power and does not require AC power. It consists of power generation and distribution subsystems. Electrical power is sourced from external power, battery power, or generator power.
The VSKYLABS 902X-NTR power source consists of a main battery and two generators.
The VSKYLABS 902X-NTR power source consists of a main battery and two generators.
PERFORMANCE & SPECIFICATIONS:
The following performance figures are based on the MD-902 flight manual. These are brought here as a reference for the VSKYLABS 902X-NTR simulation in X-Plane 12.
For more detailed performance information and data, the MD-902 manual can be used as a reference.
For more detailed performance information and data, the MD-902 manual can be used as a reference.
Important Disclaimer:
- The MD-902 RFM is an external document, unrelated to VSKYLABS.
- The provided link is for educational and informational purposes only.
- VSKYLABS is not responsible for the content, accuracy, or availability of this manual.
- The VSKYLABS 902X-NTR is not an official or exact simulation of the MD-902.
- Link: https://pscorp.ph/wp-content/uploads/2019/06/csp-902rfm206e-1_i2r6p-09.09.2009.pdf
Weight, Altitude and service ceiling:
- Maximum Gross Takeoff Weight (MGTOW): ~6,770 lbs (3,070 kg)
- Useful Load: ~3,395 lbs (1,540 kg)
- Hover In Ground Effect (HIGE): ~10,650 ft
- Hover Out of Ground Effect (HOGE): ~8,870 ft
- Service Ceiling: ~20,000 ft
Airspeed Limits and Cruise Performance:
- Maximum Cruise Speed: ~131 knots (~151 mph / 243 km/h)
- Maximum Dash Speed: ~135 knots (~155 mph / 250 km/h)
- Vne (Never Exceed Speed): ~140 knots (~161 mph / 259 km/h)
- Best Rate of Climb Speed (Vy): ~65-75 knots, depending on weight and conditions
- Rate of Climb: ~2,120 ft/min
Fuel Specifications (Without Auxiliary Tank):
- Usable Fuel Capacity (Main Tanks Only): ~127 US gallons (~481 liters)
- Fuel Burn at Cruise: ~350-400 lbs/hour (~53-60 gallons/hour)
- Range (Main Tanks Only, No Reserve): ~265-275 nautical miles (~305-320 miles / ~490-515 km)
- Endurance (Main Tanks Only, at Cruise Power): ~2.0 - 2.3 hours
General Performance Figures
ABBREVIATED CHECKLIST (MD902 REFERENCE)
ELECTRICAL POWER - OFF
All cabin doors - CHECK
Seat belt and shoulder harness - FASTENED
Rotor brake - STOWED
Flight instruments - CHECK STATIC POSITION/SET
Collective friction - ON
Collective stick position - FULL DOWN
Twistgrip alignment marks aligned with index mark - CHECK
LDG/HVR lights - OFF
Key switch - ON
Circuit breakers - IN
Utility panel switches - OFF EXCEPT VSCS ON
NACA inlet switch - AS REQUIRED
Lighting control panel switches - AS REQUIRED
Avionics - AS DESIRED
L GEN and R GEN - ON
POWER - OFF
L BOOST AND R BOOST - OFF
LEFT/RIGHT FUEL SHUTOFF - ON; COVER CLOSED
L ENGINE and R ENGINE - OFF
902eX - EXTENDED RANGE TANKS PRESS - BOTH OFF
Seat belt and shoulder harness - FASTENED
Rotor brake - STOWED
Flight instruments - CHECK STATIC POSITION/SET
Collective friction - ON
Collective stick position - FULL DOWN
Twistgrip alignment marks aligned with index mark - CHECK
LDG/HVR lights - OFF
Key switch - ON
Circuit breakers - IN
Utility panel switches - OFF EXCEPT VSCS ON
NACA inlet switch - AS REQUIRED
Lighting control panel switches - AS REQUIRED
Avionics - AS DESIRED
L GEN and R GEN - ON
POWER - OFF
L BOOST AND R BOOST - OFF
LEFT/RIGHT FUEL SHUTOFF - ON; COVER CLOSED
L ENGINE and R ENGINE - OFF
902eX - EXTENDED RANGE TANKS PRESS - BOTH OFF
ELECTRICAL POWER - ON
POWER - BAT ON
Monitor BIT - CHECK ANNUNCIATORS
Fuel quantity display - CHECK
DISP (display by exception) - AS DESIRED
Monitor BIT - CHECK ANNUNCIATORS
Fuel quantity display - CHECK
DISP (display by exception) - AS DESIRED
ENGINE STARTING - AUTOMATIC
L BOOST or R BOOST - ON; CHECK IIDS INDICATIONS
EEC MAN indicators - OFF
L ENGINE or R ENGINE - SET TO IDLE, ENGINE STABILIZED
L ENGINE or R ENGINE - SET TO FLY AS REQUIRED
IIDS - CHECK FOR NORMAL INDICATIONS
Repeat starting procedure for second engine
EEC MAN indicators - OFF
L ENGINE or R ENGINE - SET TO IDLE, ENGINE STABILIZED
L ENGINE or R ENGINE - SET TO FLY AS REQUIRED
IIDS - CHECK FOR NORMAL INDICATIONS
Repeat starting procedure for second engine
ENGINE RUNUP
Avionics - ON, AS DESIRED
L ENGINE and R ENGINE - FLY
902eX - EXTENDED RANGE TANKS PRESS - BOTH ON
L ENGINE and R ENGINE - FLY
902eX - EXTENDED RANGE TANKS PRESS - BOTH ON
BEFORE TAKEOFF
Cyclic control - CHECK RESPONSE
Collective friction - AS DESIRED
Primary and sec. IIDS displays - CHECK ADVISORIES
Utility panel switches - AS REQUIRED
Collective friction - AS DESIRED
Primary and sec. IIDS displays - CHECK ADVISORIES
Utility panel switches - AS REQUIRED
TAKEOFF
Hover area and takeoff path - CLEAR
Hover power - NOTE TORQUE
Takeoff - PERFORM, USING UP TO 10% ABOVE HOVER POWER
Hover power - NOTE TORQUE
Takeoff - PERFORM, USING UP TO 10% ABOVE HOVER POWER
CRUISE
IPS switch (if Inlet Particle Separator installed) may be turned OFF.
NOTE: Decision to use the inlet particle separator scavenge air should be based on atmospheric conditions, gross weight and height above terrain where operations are to be conducted.
NACA doors (if installed) may be closed if blowing dust, sand, etc. is present in the atmosphere.
NOTE: Decision to use the inlet particle separator scavenge air should be based on atmospheric conditions, gross weight and height above terrain where operations are to be conducted.
NACA doors (if installed) may be closed if blowing dust, sand, etc. is present in the atmosphere.
SLOW FLIGHT/APPROACH
Observe controllability envelope and critical wind azimuth as stated in Section II.
The NACA door actuators (if installed) receive a discrete input from an airspeed switch in the airspeed indicator. This signals the NACA doors to automatically close. When airspeed increases above 47 KIAS, the NACA doors open. If the door actuator fails to function properly, the IIDS will display ‘‘NACA DOOR’’ advisory message in the alphanumeric display.
The NACA door actuators (if installed) receive a discrete input from an airspeed switch in the airspeed indicator. This signals the NACA doors to automatically close. When airspeed increases above 47 KIAS, the NACA doors open. If the door actuator fails to function properly, the IIDS will display ‘‘NACA DOOR’’ advisory message in the alphanumeric display.
LANDING
Use the illustration below to determine safe landing attitudes. Nose up attitudes in excess of 9° 40′ will result in the tail skid contacting the landing surface.
Tail Skid to Landing Surface Clearance
Running landing:
Maximum recommended ground contact speed is 30 knots for smooth hard surfaces.
Avoid rapid lowering of the collective and aft cyclic after ground contact.
Slope landing:
Slope landings have been demonstrated up to 12° in any direction. Successful
completion of this maneuver on a particular surface will depend on sufficient
friction between the skid tubes and the landing surface to prevent the helicopter
from sliding.
Maximum recommended ground contact speed is 30 knots for smooth hard surfaces.
Avoid rapid lowering of the collective and aft cyclic after ground contact.
Slope landing:
Slope landings have been demonstrated up to 12° in any direction. Successful
completion of this maneuver on a particular surface will depend on sufficient
friction between the skid tubes and the landing surface to prevent the helicopter
from sliding.
ENGINE/AIRCRAFT SHUTDOWN − NORMAL
Collective stick - FULL DOWN/FRICTION ON
Cyclic stick - TRIM TO NEUTRAL
Pedals - NEUTRAL
L ENGINE and R ENGINE - IDLE
902eX - EXTENDED RANGE TANKS PRESS - BOTH OFF
All unnecessary electrical equipment - OFF
Heat - OFF
AC (if installed) - OFF
Pitot heat (if installed) - OFF
IPS (if installed) - OFF
Lighting control panel - AS DESIRED
Avionics master switch - OFF
L GEN/R GEN switches - OFF
L BOOST/R BOOST - OFF
L ENGINE and R ENGINE - OFF
ENG OUT indications - CHECK IIDS FOR NORMAL INDICATIONS
Rotor brake (if installed) - APPLY BELOW 70% NR
IIDS - CHECK FOR INDICATIONS OR MESSAGES
POWER - OFF
Cyclic stick - TRIM TO NEUTRAL
Pedals - NEUTRAL
L ENGINE and R ENGINE - IDLE
902eX - EXTENDED RANGE TANKS PRESS - BOTH OFF
All unnecessary electrical equipment - OFF
Heat - OFF
AC (if installed) - OFF
Pitot heat (if installed) - OFF
IPS (if installed) - OFF
Lighting control panel - AS DESIRED
Avionics master switch - OFF
L GEN/R GEN switches - OFF
L BOOST/R BOOST - OFF
L ENGINE and R ENGINE - OFF
ENG OUT indications - CHECK IIDS FOR NORMAL INDICATIONS
Rotor brake (if installed) - APPLY BELOW 70% NR
IIDS - CHECK FOR INDICATIONS OR MESSAGES
POWER - OFF
